Apparatus for treating articles



1 192 May 7 7 H. M. ROBERTSON APFARATUS FOR TREATING ARTICLES Filed May 2, 1925 8 Sheets-Sheet 1 l f/N/ ,f1/of,

NN mW mm, e6 m5 May 17 1927 H. M. ROBERTSON APPARATUS FOR TREATING ARTICLES Filed May 2, 1925 8 Sheets-Sheet 2 Syvum/Hoz May 17 1927' H. M. ROBERTSON APPARATUS FOR TREATING' ARTICLES Filed May 2, 1925 8 Sheets-Sheet 3 @Ronny .MJ KNMI.

May 17, 1927.

H. M. ROBERTSON APPARATUS FOR TREATING ARTICLES 8 Sheets-Sheet 5 Filed May 2, 1925 1 9 1628,742 May 7 l 27 H, M. ROBERTSON APPARATUS FOR TREATING ARTICLES Filed May 2. 1925 8 Sheets-Sheet 6 May 17, 1927. 1,628,742

H. M. ROBERTSON APPARATUS FOR TREATING ARTICLES Filed May 2, 1925 8 Sheets-Sheet 7 UNET HARRY M. BOBEBTSGN, OF LAKEWOQD, 0R10.

APPARATUS FUE, TBEATNG LRTICLES.

Application filed. May a,

This invention relates to an apparatus for treating, heating or annealing articles or bodies, more particularly to an apparatus or' Vthe continuous tunnel kiln type having a driven conveyor, which passes through a heating zone or furnace section, and thus conveys the articles or bodies to be treated therethrough.

One object of the invention is to provide an improved apparatus of this type wherein various kinds of articles or materials may be uniformly' and economically treated.

Another object of the invention is to provide an improved treating apparatus so constructed that the articles or bodies may be treated Without being subjected to the gases of combustion.

Another object of the invention is to construct an improved furnace having a pair of combustion chambers arranged in spaced relation to form a heating chamber or zone between them for the articles or bodies to he treated.

Another object of the invention is to pro-r vide a heat treating apparatus having improved heht generating chambers, whereby the heat zone throu h which the bodies to be treated are passe may be maintained at any predetermined temperature in an ecoiioinical manner.

Another object of the invention is to construct an improved furnace of this character wherein provision is made for readily varying the temperature of the heating chamber and eriod of treatment of the articles depending upon the nature, character and construction thereof.

A further object of the invention is to construct a furnace in which the walls of the heating or Ytreating zone have relatively high radiating properties and are arranged. to provide two channels at either side of the zone, both extending from end to end thereof without contacting with the products being treat-ed and'to preheat the air utilized for combustion,whereby a high temperature may be attained with economical fuel consumption.

Other objects of the invention wvji be apparent to those skilled in the art to which my invention relates from the following de scription taken in connection with the accompanying drawings, wherein:

Fig. 1 is a horizontal sectional View of an apparatus embodying my invention, the

1925. Seri-a1 No. 27,616.

Fig. 8 is a vertical section on the line 8s-8 of Fig. 9.

'Fig'. 9 is 'a section on the lines 9-9 of Figs. 7 and 8.

Fig. 10 is a section on the line 10-10 of Y Fig. 8.

Fig. 11 is a vertical section on the line 11-11 o Fig. 12 showing another form of construction embodying my invention.

Fig. 12 is a section on the line12-12 of Fig. 11.

Referring to Figs. 1 to 6, inclusive, 1 indicates a bed preferably formed from concrete and being of sullicient area to provide a base for the entire apparatus. Thebed 1 is of different Widths between its iront and rear ends, dependent upon the size of the furnace or treating section indicated as an entirety at 2 and inlet and cooling sections 3, 4, of the structure, (where the latter are incorporated therein, as shown in Figs. 1 to 6, inclusive) to be later described. The bed 1 may be supported in any desired Inan ner, either upon a suitable foundation, or upon longitudinal walls (such as illustrated in Figs. 8, 9 and 10), or upon longitudinal and transverse sills (such as shown in Figs. 11 and 12). In either form of construction a space or chamber 5 is provided below and extending longitudinally and centrally of the bed, the purpose of the chamber being .to provide a space forthe lower or return run of a conveyor 6 and an economical means for cooling the conveyor while passing from the discharge end of the apparatusl to its inlet end. l

The bed 1 is provided with a central sec= tion 18L for the furnace section 2 and extensions l", 1, for the inlet and cooling sections 3, e, respectively. -The chamber 5 is preferably provided with a bottom wall 5,

side Walls and ,tend walls 5, The end Walls 5c arefspaeed from the opposite ends ofthe bd/ 1 to form suitable openings through which the conveyor passes as it swings from one run to the other. This arrangement permits the upper run of the conveyor to move through the sections 3, 2, 4, upon the bed 1 and its lower run to return therebelow, so that the bed 1 serves to protect the lower run from the heat of the furnace section 2 of the apparatus, thus allowing the conveyor to cool as it passes to the inlet end. As the chamber 5 is sunk below the bed and disposed within the foundations therefor, it is well insulated from the heat generated within the furnace section and radiating therefrom. By providing openings at the opposite ends of the chamber 5, a circulation'of air therethrough is provided for, the movement of the conveyor 6 tending to induce this circulation through the chamber. The walls 5, 5* and 5' are preferably formed from concrete and may be constructed integrally with the bed 1, as shown in Figs. 3, 4- and 5.

The furnace section 2 comprises a heating chamber 7 through which the upper run of the conveyor 6 extends so as to convey the articles or bodies to be treated therethrough, main combustion chambers 8 disposed along opposite sides and extending fromend to end of the heating chamber 7, and a separate combustion chamber 8 also extending from end to end of the chamber and connected to the main chambers 8. The chamber 7 is formed between upstanding walls 9, 9, and an arch 9', whereas each chamber 8 is formed between one Wall 9 and a wall 10, the latter being incorporated in and forming the main or outer side wall of the furnace section 2, and a cover 1nember 10.

As will be understood from Figs. 3 and G, the arch. 9 and cover members l0 serve as the walls between the separate combustion chamber 8 and lthe heating chamber and main combustion chambers 8, respectively; the cover members 10 being formed with spaced transverse openings 11 disposed at the rearward ends ot the chambers 8 (see Fig. 6), so that the gases and products of combustion after passing through the latter chambers and along the side walls 9 of the heating chamber' 7, pass up into the separate combustion chamber 8, where they are reversed and pass along the arch 9 to the front end of the latter chamber. finally escaping through the port 12 (see Fig. 2). The separate combustion chamber is disposed above and is common to the heating chamber 7 and the combustion' chambers 8, being formed between the arch'9, members 10 and an arch 8b supported along its opposite sides by the walls l0, 10, and closed at its opposite ends by end walls 8c. The combustion chambers 8 are provided with end walls 8' which extend inwardly from the side walls 10V and are connected to and incorporated with the walls of the inlet section 3 and cooling section 4. The Walls 9 and 10 may be insulated from the bed 1 by suitable non-heat conducting material 13. The outer faces ofthe walls 10 maybe insulated by walls of nonheat conducting material 14, which together with the adjacent walls may be jacketed b bricks of fire clay or other suitable materia?, as shown at 15. 16 indicates a plurality of stays or uprights suitably fixed in the bed 1 and extended upwardly along the outer sides of the jacket 15, their upper ends being connected by tie rods 17, in any desired manner. more horizontal slabs 9u and superimposed bricks 9b having a relatively high co-efhcient of heat conductivit so as to readily radiate the heat absorbed rom the combustion that takes place in the chambers 8. The uppermost bricks of the walls 9 are formed with recesses to provide seats for the wall 9', which is preferably of arch shape. The bricks of the upstanding-Walls 9, 1.0, are preferably arranged to form projecting ledges 18 upon which the cover members 10' rest, as shown in Figa/3.

The arch 8* may be constructed from suit able fire brick (shown dia raxnmatically in the drawing), and covere lwith a suitable non-heat conducting and insulating material 8d. By preference the bricks 9t7 and arch 9 may be formed from alundum or carbotrax, both well known manufactured materials', whereas the insulatin Walls 13, let, may be formed from what is nown as celite.

1n the form of construction being described, the heating means, indicated as an entirety at 19, for each combustion charnber 8 is arranged at the front end thereof (having reference to the inlet end of the apparatus), so that the products or combustion move through the chamber te its rear end and then ass through the openings 11 (see Fig. 6) ormed in the adjacent cover member 10 to the separate combustion chamber 8"; then they return in contact with the arch or cover member 9" to the front end of the furnace section, finally escaping through the exit or fine 12, as aiready set forth.

19 indicates a conduit for the supply oi air to each ofthe chambers 8. Each conduit 19 extends from the rear end of the furnace section to its front end. below the adjacent combustion chamber 8, the 'purpose being to pre-heat the air before it is introduced into the combustion chamber. At or near its rear end, the conduit has a lateral port 19 through which extends a pi e 19" that supplies air from a point out-si e the wall 10. The air conduit 19 is formed be= tween the walls 9, 10, and separated from Each wall 9 consists of one or the adjacent combustion chamber 8 by a re1- atively thin slab of non-combustible material 20, but preferably having a relatively high co-eificient of heat conductivity, such as alundum or carbofrax, already referred to. At or adjacent the front end of the air conduit 19', the slab 20 is formed with an openin 21 through which the heated air passes to t ie combustion chamber 8. In the form of construction just described (see Fig. 1), it will be seen that the air enters the air conduit 19 at a point adjacent the rear end of the combustion chamber 8 and flows the entire length thereof before entering into /the chamber. As a result, the air is heated to a relatively high temperature before being admitted to the combustion chamber 8.

The heating means 19, in the illustrated form of construction for each chamber 8, comprises an oil burner of any desired type and construction, having a mixing chamber terminating in a suitable nozzle 19a', which projects into a suitable opening 19h formed in the adjacent wall 8. The burner is connected with a valved supply pipe leading to a source of supply.

The inlet section 3 preferably comprfses side walls 22 supported on the bed 1 and spaced to form a passage 3 in alignment ywith the heated zone or chamber 7, and a top wall 23, preferably of arch shape, supported on the upper ends of the walls 22. As shown in F ig.` 4, the walls 22 are reinforced and insulated by suitable tire-brick 22',y and these in turn are braced by stays 24 that may be supported similarly to the stays 16. 25 indicates a door adapted to extend across the entrance end of the passage 3 to restrict the opening thereinto so as to admit the conveyor 6 and articles or bodies positioned thereon for treatment; the supports (not shown) for the door 25 being arranged to permit its adjustment. The door 25 may carry on its lower edge chains which serve as ballies to prevent the flow of air into the inlet section.

The cooling section 4 preferably comprises side walls 26 supported on the bed section 1c and spaced to form a passage 4 in alignment with the heated zone or chamber 7 so that the conveyor 6 may pass directly into and through the cooling section to the discharge point for the treated arti cles, and a flue 27 supported upon and pret'- erably extending substantially from end to end of the side walls. The flue 27 comprises a hollow casing having an opening 27 at its rear end and an, outlet or discharge pipe 28 connected to its front portion. The pipe 28 may enclose an exhaust fan, driven by a motor or other form of power means to induce a circulation of air through the opening 27 into the flue and out through the pipe 28. In the preferred form of construction I utilize the cooling section 4 to cool the articles or bodies, after passing through the heated zone or chamber 7, down to a temperature that is below the scaling point thereof, before they are subjected to normal atmospheric conditions; although it will be obvious that where the bodies do not have to be cooled down, the cooling section 4 can be omitted. 25 indicates a door at the discharge end of the cooling section 4, preferably constructed and adjustably supported in a manner similar to the door 25, to control the space or exit from the passage 4.

The conveyor 6 preferably comprises a pair of endless chains 6, certain links of which (preferably alternate links) are provided with aligned laterally extending bars 6", each bar of which is connected by a suitable supporting element 6c for supporting the articles or bodies to be treated while the upper run of the conveyor is passing through the passage 3', chamber 7 and passage 4. The supporting elements 6c may be of any desired shape and construction, depending upon the shape and construction of the articles to be treated, but are referably rigidly connected to the bars 6b 1n a wellknown manner. The endless chains 6a engage with and run around suitable sprockets 29 mounted on shafts 30, 30', which are supported in suitable bearings in the side walls 5*. The sprockets 29 on one shaft are rigidly connected thereto so that power may be applied to the shaft and through it operate the conveyor 6. For this purpose, the shaft 30 at the discharged end of the conveyor 6 is extended laterally and provided with a worm gear 3l with which meshes a worm 32 on the shaft of a variable speed motor 33, whereby the shaft 30 may be driven at any desired rate of speed to move the conveyor' through the heated zone or chamber 7 at a relatively fast or a relatively slow rate of speed, as desired. It will be understood that the motor 33 is shown merely for illustrative purposes, since any desired form of power means may be readily adapted to the driving of the shaft 30. The other shaft 30 is preferably mounted in a pair of bearing blocks 34 which slidably engage guides 35 secured to the side walls 5*. The blocks 34 are engaged by screws 36, the adjustment of which operates to slide the blocks along the guides 35 so that slack in the chains 6, due to wear or stretching, may be readily taken up.

The chains 6'vl are preferably provided with suitable rollers 37 which engage with and run on tracks 38 mounted in and extending through the chambers 3', 7, and 4. and tracks 39 supported upon the .side walls 5b and extending substantially from end to end of the chamber 5. The tracks 38 preferably comprise channel bars each Supported upon one or moreconduits 40 through which a cooling medium, such as water, is circulated, so as to maintain the chains and rollers and the inner ends of the bars 6b relatively cool. The conduits 40 are preferably in the form of rectangular shaped pipes (two thereof being preferably provided below each track) so that they may be arranged in side by side relation upon the bed l or, a plate 41, as shown in Fig. 3. The tracks 38 extend from end to end of the bed l. The tracks 39 may comprise angle bars fixed to the side walls 5b in any desired manner.

42 indicates a wall extending longitudinally of the bed 1 between the tracks 38. The wall 42 may extend from the front end of the inlet section 3 to or slightly beyond the rear end of the furnace section 2 (see Fig. 2). The height and width of the wall 42 is such that the bars 6l and' supporting elements 6C move through the inlet section 3 and the heating chamber 7 without engagement therewith. The opposite sides of the wall 42 are spaced from the inner faces of the wall 9 sufiiciently to provide ample space for the movement of the bars 6b. The Wall 42 is formed of several layers of slabs or bricks, preferably of different non-heat conducting materials, the purpose being to protect the endless chains (5Ct and bars (3h from the heat of the furnace section 2, so far as possible. To further accomplish this advantageous result, the slabs 9a preferably project inwardly to provide an inset chainber 43 and the bars 6 are offset at their inner ends as shown at 44, so that the chains 6a may be arranged under the projecting portion of the slabs 9a, and be rotected thereby from the heat radiating rom the walls 9 and 9'. The walls 22 and 26 of the inlet and cooling sections are constructed to provide a continuation of the chamber 43 through them, will be understood from Figs. 4 and 5.

As will be understood from Figs. 1 and 2, the sections 1b, l, of the bed l extend beyond the inlet section 3 and the cooling section 4, the front extension providing ample room and space. for the laying of the articles and bodies on the connecting bars 6 of the conveyor o as they move toward and into the inlet section 3 and the rearward extension providing 'space for the removal of the article; or bodies from the bars 6, unless provision is made for their automatic discharge as shown in other forms of my invention to be later referred to.

Referring to Figs. 7, 8, 9 and l0, 45 indicates the bed mounted on longitudinally disposed walls 46, 46, 46a, 46, the latter walls forming the return channel or space 5 (already referred to) for the conveyor 6. 4T indicates the heated zone or furnace section and 48 indicates the inlet section connected thereto. The furnace section 47 comprises a heated chamber 49 through nected to the main chambers 50 at their front ends by openings (not shown) similar to the openings 11 shown in Fig. 6, so that the products of combustion may pass from the chambers 5() to chamber 509, 50b indicates the outlet from the chamber 50". 51, 51, indicate conduits or chambers for supplying air to the main combustion chamf bers 50. These conduits 51 have air inlets at their front ends, preferably similar to those shown in Fig. l for the conduits 19.

The conveyor 6 is similar to the conveyor 6, but is shown provided With a different form of article carrying bars 6. The conveyor chains are guided and supported by pairs of sprockets. the pair at the delivery end of the furnace section being arranged within the heated zone 49 and arranged to discharge the articles or bodies downwardly through an opening 52 formed in the bed 45. articles; this hopper may be provided with a removable receptacle 53 or a conveyor to cai-ry the articles awayi Above the hopper 53 is a chute 54 which guides the articles to the hopper. By preference, one wall 54a of the chute 54 may be adjusted to the position shown in dotted lines in Fig. 8, so that the articles may be guided to a point exterior of the hopper 53.

As shown in Fig. 9, the chambers and conduits referred to and constituting the furnace section 47 all formed by walls, substantially siniilar in construction to like walls shown in Figs. l, 2 and 3, but in illustrating this form of construction I have made the furnace section somewhat longer and reversed the paths traversed by the air and by the products of combustion. The inlet section 48 is substantially similar in construction to the inlet section 3 and its walls are connected to and incorporated with the walls of the furnace section in any desired manner. The walls of these sections are insulated with suitable refractory materials, as shown at 55, 56, in a manner similar vto that shown in Figs. l, 2, 3 and 4.

The furnace section 47 is provided with au end wall 48a in which are formed openings 48b (see Fig. 7) arranged to receive suitable burners (not shown) preferably adapted to burn oil or gas and connected with a suitable source of supply.

48C indicates an opening leading through the wall 48a into the heatedzone to permit inspection thereof and view of the articles while being treated. At its outer end, the

53 indicates a hopper for receiving the opening is provided with a suitable cover 48 25* indicates a door for the inlet section 48. The door 25a is supportedy for adjustment to different positions so as to freely admit 'the conveyor and the articles supported on it. i

Figs. 11 and 12 show a further modified form of construction, but somewhat more simplified, for treating bodies where ythe heating means comprise resistance elements connected with a suitable source of electric supply. In this form of construction I have also shown the apparatus as mounted on a frame and the entire apparatus may be moved from one place to another.

In these views, ythe frame 57 preferabl comprises a pair of longitudinally exten ing channel bars 57 a and a plurality of cross bars (such as I beams and channel bars) 58 resting on and connected at their o posite ends to the bars 57. 59 indicates the bed for the apparatus, comprising a flooring 59 and a layer of concrete or other suitable material 59h. 60 indicates the furnace sec tion comprising side walls 61, 61, a top wall 62 and a rear wall 63, and forming between then a heated zone 60. 64 indicates a resistance or plurality of resistances mounted on suitable supports 65 projectin from the inner face of each side wall 61 an connected in any desired manner with leads (not shown) which in turn are connected to the electric supply mains; or if desired the current for the resistances 64 may bevsupplied from a generator 65, preferably driven by an electric motorv 66. The resistance 64 on each wall is supported in vertical sections to provide a maximum length thereof and thus insure the necessary degree of temperature within the zone 60.

The walls 61, 62 and 63 are formed from suitable refractory bricks and slabs and' these in turn may be insulated and reinforced by concrete or other suitable material as clearl shown in Figs. 11 and 12.

6* in icates the conveyor which is constructed and guided in a manner substantially similar to that shown in Figs. 1 to 10, inclusive, except that the space 5 is formed by the channel bars 578| and the guides 37a for the lower run are supported by the cross bars 58 (see Fig. 12).

The chains 6" of the conveyor run on pairs of sprockets 66, 67, the latter pair being arranged within the zone 60', so that the conveyor discharges the articles when treated downwardly through an opening 59" formed in the bed 59 into a chute 68 which delivers the articles at some suitable posi-v tion or station for removal. The chute 68 may be provided with a gate or hinged section 68a arranged to be swung upwardly whereby the articles may be discharged at a point below the chute.

The pair of sprockets 66 may be adjusted by a pair of screws 6,9 (one being shown in Fig. 11), which engage the bearing blocks for the shaft 70, suitable guides 71 for the blocks being provided on the frame 57. The chains 6" support thebody carrying devices 72 which, in this form of construction, may comprise troughs.

73 indicates a door slidably supported on the front wall of the furnace and arranged to be adjusted to control the size of the entrance to the furnace section.

The conveyor 6X is driven by the follow ing instrumentalities: 74 indicates a ratchet fixed to the shaft a for the sprockets 67. 75 indicates a rod carrying a pawl 76 arranged to engage the ratchet 74. The upper end of the rod 75 is connected to an eccentric 77 which is operated by the shaft for the motor 66. These instrumentalities serve to move the conveyor step by step; altho I may provide a drive means which will move the conveyor uniformly.

In this last described form of construction I have shown a unitar arranged that it may be bodi y moved from one place to another. 'By using resistances as a means of heating, the degree of temperature may be regulated or controlled in a ready and well known manner.

In operation, the articles or bodies to be heat treated are placed on the supporting bars or devices, that are connected to and moved by the conveyor, outside of the inlet section; the conveyor moves the articles into and through the inlet section and then the furnace or heated section which is contiguous thereto; and finally through the cooling section as shown in Fig. 2 or to some other point of discharge. It will thus be seen that I have provided a movin hearth which conveys the articles or bo ies into and through the furnace, first throu h the inlet section where they are gradually cated and then between a pair of combustion chambers having a maximum temperature.

The heated zone may be made of any desired length. By constructing the combustion chambers to cause the products of combustion to traverse this zone twice and supplying to the combustion means preheated air, I am enabled to secure a relatively high tempera ture at minimum cost and to keep the tempcrature uniform and constant from end to end of the heated zone, uniform treatment of the articles or bodies. By providing combustion chambers at both sides of the heated zone and thereabove, and constructing the walls for these chambers of a material which has a high co-eticient of heat conductivity, a maximum temperature ma be readily maintained.

t the same time the construction prevents the products of combustion from coming in contact with the articles or bodies.

structure sothereby insuring By regulating the speed of the conveyor, the period of treatment can be regulated at will To those skilled in the art of making apparatus ot this character, many changes in construction and widely diti'ering embodiments and applications of the invention will suggest themselves Without departing from the spirit and scope thereof. My dislosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

My apparatus is adapted for use in the treatment of metal parts or bodies, such as bolts, nuts, plates, strips and shaped articles, where heat treating (for example, annealing) is desired; also for baking enamel covered parts and bodies. The apparatus may also be used by baking bodies formed of clay and similar material.

The heated chamber may be heated to a temperature, as desired, ranging up to 200() degrees Fahrenheit. By providing an inlet section in contiguous relation to the heated section the bodies first pass through a chamber that enables them to be partially heated before being conveyed into and through the heated chamber. Likewise, the cooling chamber permits the bodies to be cooled be fore they are subjected to the normal temperature, thereby preventing scaling and distortion of the bodies.

What I claim is:

1. In apparatus of the class described, the combination of a bed, inlet and heated sections on said bed correlated to form contiguous chambers, whereby bodies to be treated may be passed therethrough, a pair of spaced Walls at either side of the chamber, horizontal members forming with said walls a combustion chamber and an air conduit having an air inlet and a discharge port leading into said combustion chamber, a heating means at one end of each said combustion chamber, and means for conveying the bodies through said contiguous chambers.

2. An apparatus as claimed in claim 1 in which the`air inlet for each air conduit is at the end thereof opposite to the heating means in the adjacent combustion chamber.

3. In apparatus of the class described, the combination of a bed, inlet and heated sections on said bed correlated to form con-- tiguous chambers, whereby bodies to be treated may be passed therethrough, a pair of spaced walls at either side of the chamber, horizontal members forming with said walls a combustion chamber and an air conduit having an air inlet at its rear end and a discharge port at its front end leading into said combustion chamber, a heating means at the front end of each said combustion chamber, and means for conveying the bodies through said contiguous chambers.

4. In apparatus of the .class described,

the combination of inlet, heated and cooling sections disposed in end to end relation to form a chamber through which bodies to hc. treated are passed, said heated .section coniprising inner and outer walls at. either sido of said treating chamber and extending from end to end of the heated section. upper and lower horizontal members extending bctween each outer Wall and the adjacent innen wall and forming a combustion chamber and an air supply chamber, said lower member being formed with an opening through which air passes to the adjacent combustion chamber, and a heating means in each said combustion chamber.

5. An apparatus as claimed in claim 4 in which the air opening and the heating means are disposed at the corresponding ends of the combustion and supply chambers.

6. An apparatus as claimed in claim 4 in which the cooling section is provided with a Hue having an inlet opening at its outer eng and a discharge opening at its inner en 7 An apparatus as claimed in claim 4 in which the cooling section is provided with a tine having an inlet opening at its outer end and an exhaust mechanism connected to its inner end.

8. In apparatus of the class described, the combination with a bed and outer walls, of a pair of inner walls on said bed spaced to form a passage between them, a horizontal wall between each outer wall and the adjacent inner wall to form a main combustion chamber extending from end to end of said passage, a roof member extending between said inner walls and co-operating therewith to form a closed passage, a roof member extending between. said outer walls and forming with said first mentioned roof member a separate combustion chamber common to both said combustion chambers and superposed above said treating passage, each said horizontal wall being formed near one end with an opening through which the products of combustion pass to said separate combustion chamber and the latter being formed with a discharge port, a heating means at the end of each main combustion chamber opposite to the outlet opening therefrom, and means for conveying bodies to be treated through said passa e.

In apparatus of the class described, the combination of a bed and outer walls, a

air of inner walls on said bed spaced to erm a assage between them, arches extending between said inner walls and between said outer walls to close said passage and form a combustion chamber between said arches, cover members between each outer wall and the adjacent inner wall to form a main combustion chamber and an air supply chamber, each of said members lll being formed with an opening, said openings being at the opposite ends of said members and one serving as an inlet to admit air to said main combustion chamber and the other serving as an outlet to dischargeI the products of combustion from the latter` to the first mentioned combustion chamber, a heating means in cach main combustion chamber at that end thereof adjacent the air inlet opening, and means for conveying bodies through said passage.

10. An apparatus as claimed in claim 9 in which the arch between the outer walls is formed with a discharge port at that end opposite to the opening for the products of combustion thereinto from the vmain combustion chambers.

11. An apparatus as claimedin claim 9 in which the conveying means comprises an endless conveyor the upper run of which moves over said bed and its lower run returns therebelow.

In testimonj whereof, I have hereunto subscribed my name.

HARRY M. RCBERTSON. 

